Note 6 - Stockholders' Equity and Stock-based Compensation - Option Assumptions (Details) - Share-Based Payment Arrangement, Option [Member]	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Expected volatility		78.00%	70.00%
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Expected term in years (Year)	5 years 3 months 18 days	5 years 3 months 18 days	5 years 3 months 18 days
Risk-free interest rate	1.90%	0.90%	0.30%
Maximum [Member]
Expected term in years (Year)	6 years 9 months 18 days	6 years 1 month 6 days	6 years 1 month 6 days
Risk-free interest rate	3.20%	1.40%	0.50%